Difficult one to answer. The only form I have seen this question asked on is the Class 1 medical renewal /issue questionaire.
Any history of accidents may be pertinant to an employer from an insurance point of view. As such witholding that information would almost certainly amount to a failure to disclose relevant and important information. I think you must therefore disclose the fact prior to starting employment. However I cannot really say if this should be brought up at interview or if you should disclose it after an offer of employment has been made. Certainly if you did the latter it would confirm or dispel your doubt.